You can nip the constipation in the bud by getting on colace and fiber at the same time. It's a hassle to take so many pills, and it comes with it's share of guilt, but it's a lot safer than dehydration/malnutrition.

Ditto this whole post. Zofran will be okay if you stay on top of the constipation. I'm on high doses of Miralax, fiber and Magnesium and as long as I take 'only' 24mg (3x8mg pills) of Zofran I'm okay. I can't do the 32mg max dose or I am constipated even then. Thankfully the 24mg is enough to keep me hydrated and I have managed to gain back 8lbs of the 15 I lost. If you are not keeping down anything you need something. And if you can't keep down pills you need the meds through IV or suppository.

(MommaLEB you post on the HG forums too right? I have the same username there)